1. Technical Field
The present invention relates to computer networking.
2. Description of the Related Art
Data management within organizations is an ever increasing concern, especially with the rise of the Internet information age. The heart of this data management function is sometimes known as a data center. Over the last decade, data centers have evolved into the strategic focus of Information Technology (IT) efforts to protect, optimize, and grow the organization.
Data center managers face several challenges in fulfilling these goals. Most enterprise data centers grew rapidly to meet the explosive economic growth of recent times. Consequently, applications commonly stand alone in underutilized, isolated infrastructure silos. Each infrastructure silo is designed based on the inclination of the specific application being deployed, so that a typical data center supports a broad I assortment of operating systems, computing platforms, and storage systems. The disparate infrastructures supporting different application “islands” are difficult to change or expand and expensive to manage, integrate, secure, and back up. FIG. 1 illustrates this type of “isolated application” environment.
One solution to this problem is to design a data center environment that is highly scalable, resilient, secure, and able to integrate multiple applications and protocols. One such solution is known as the Data Center Network Architecture. A specific implementation of the Data Center Network Architecture is known as Data Center Ethernet (DCE). DCE allows for consolidation of input and output, and improved forwarding of communications within the network. This may be accomplished via specialized protocols and functionality operated by switches within a DCE network via network layer 2. Each of the switches within the DCE network may be a layer 2 device. FIG. 2 illustrates a DCE network. Edge switch 200 may be connected to a server 202. Edge switch 204 may be connected to server 206. Edge switches 200, 204 may then be connected to several core switches 208, 210, which then may be connected to other edge switches 212, 214. Each DCE switch may be assigned a unique identifier. A routing protocol, such as Intermediate-System-to-Intermediate-system (IS-IS), may be used inside DCE. Switches using this routing protocol may append information to frames sent though the DCE. This appended information may be in the form of a MAC-in-MAC header attached to the frame. Edge switches 212, 214 may then each be connected to non-DCE devices, such as Classic Ethernet (CE) switches 216. CE switches do not run the forwarding protocols supported by DCE, and do not append the MAC-in-MAC information. They run a variant of the Spanning Tree protocol. They are connected to the DCE network.
Rather than forwarding frames to MAC addresses, DCE switches send frames to edge switches based on the edge switch identification via the MAC-in-MAC header. The edge switch then knows which of its ports to send the frame out to arrive at the correct MAC address (for example, the port connected to switch 216), and strips off the MAC-in-MAC header prior to doing so.
The network design depicted in FIG. 2, however, encounters a problem during actual operation. Specifically, when two links originate from the same CE switch 216 to different DCE switches 212, 214, the spanning tree protocols operated by CE switches recognize this as a spanning tree loop. The remedy for such a loop is to activate only one link at a time. This, however, eliminates the possibility of load sharing and providing redundancy across 2 (or more) DCE chassis.